PROJECT SUMMARY: Despite the widespread use of antiretroviral therapy (ART), the prevalence of neuro- inflammation remains high and is believed to involve >40% of HIV+ individuals. This inflammatory state likely causes cognitive dysfunction that impacts everyday functioning and increases morbidity and mortality among ART-suppressed HIV-infected individuals. However, the physiological processes underlying this neuro- inflammation remain poorly understood. This proposal builds on our ongoing investigation on whether glycomic alterations in circulating glycoproteins and exosomes play a role in the pathogenesis of HIV-associated neuro- inflammation and cognitive disorders. Our preliminary data demonstrate that higher levels of the pro- inflammatory hypo-sialylated glycans in plasma, plasma exosomes, and cerebrospinal fluid (CSF) strongly correlate with worse neurological impairment in HIV+ ART-suppressed individuals. However, whether glycomic alterations drive neuro-inflammation during HIV infection remains unknown. In this project we will test the central hypothesis that host glycomic dysregulation, in particular hypo-sialyation of circulating glycoproteins and exosomes, contributes to neuroinflammation and the pathogenesis of HIV-associated co- morbidities affecting the central nervous system (CNS). In Aim 1, we will identify the mechanism of the neuro-inflammatory effects of hypo-sialylated glycans during ART-suppressed HIV infection. We will use hyper-sialylated and hypo-sialylated glycoproteins and exosomes isolated from the plasma of HIV+ ART+ individuals with neurological impairments, in an ex-vivo model of monocyte activation/inflammation and migration, in the presence or absence of glycan signaling inhibitors. In Aim 2, we will test the hypothesis that manipulating the levels of circulating sialic acid impacts neuro- inflammation and cognitive behavior in a mouse model of HIV-associated neurological impairment. We will use the EcoHIV mouse model (using chimeric HIV capable of infecting mice) that was recently used as a successful model of HIV pathogenesis and neurological impairment. Using acutely and chronically EcoHIV-infected mice (with and without ART), that receive either a combination of sialic acid nanoparticles and sialidase inhibitors or nude nanoparticles as controls, we will evaluate: (1) levels of cognitive impairment; (2) brain markers of inflammation/immune activation [gene array and immunohistochemistry]; (3) EcoHIV expression in brain tissues [qPCR]; and (4) sialylation of brain tissues and brain-derived exosomes [lectin array and flow cytometry]. We will take advantage of recent advances in the emerging field of glycomics and an animal model of HIV-associated neurological impairment, to clarify the inter-related mechanisms between neuro-inflammation, cognitive dysfunction, and host immunity. Our work aims to create a new paradigm for discovering novel glycan- based interactions that can be targeted to prevent neuro-inflammation that persists in individuals living with HIV despite viral suppression.